Electronic device

ABSTRACT

A display device includes a light-emitting element layer on the substrate and having a display area for displaying images, and a sealing layer covering the light-emitting element layer. The sealing layer includes a first inorganic film, an organic film on the first inorganic film, a second inorganic film on the organic film, and a third inorganic film. The first inorganic film and the second inorganic film are in contact with each other around the organic film. The third inorganic film, without overlapping with the display area, covers a peripheral portion of the organic film.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese applicationJP2018-92864 filed on May 14, 2018, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This relates to display devices.

2. Description of the Related Art

A light-emitting element layer such as an organic electroluminescencelayer, which is vulnerable to moisture, needs to be covered with asealing layer to be blocked from air. One of known structures includes asealing layer having a multilayer structure, where an organic film madefrom resin is interposed between a pair of inorganic films, for sealingthe light-emitting element layer. The structure, in spite of foreignobjects included. therein, is filled with the organic film to evenirregularities, preventing a defect of the inorganic films, obtaininghigh barrier performance (JP 2007-250370A and JP 2014-154450A).

The organic film at its peripheral portion is made thinner in an outwarddirection when the pair of inorganic films are in contact with eachother around the organic film, leading to low coverage of the foreignobjects, making it unlikely to completely prevent the defect of theinorganic films. This may degrade barrier performance.

SUMMARY OF THE INVENTION

This is to aim at preventing degradation of barrier performance.

A display device includes substrate, a light-emitting element layerhaving a display area for displaying images, and a sealing layercovering the light-emitting element layer. The sealing layer includes afirst inorganic film, an organic film on the first inorganic film, asecond inorganic film on the organic film, and a third inorganic film.The first inorganic film and the second inorganic film are in contactwith each other around the organic film. The third inorganic film,without overlapping with the display area, covers a peripheral portionof the organic film.

The third inorganic film may prevent deterioration of barrierperformance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a display device in an embodiment.

FIG. 2 is a schematic view of the display device in use.

FIG. 3 is a III-III line schematic cross-sectional view of the displaydevice in FIG. 2.

FIG. 4 is a IV-IV line cross-sectional view of the display device inFIG. 1.

FIG. 5 is a circuit diagram of the display device in FIG. 1.

FIG. 6 is a VI-VI line cross-sectional view of the display device inFIG. 1.

FIG. 7 is a VII-VII line cross-sectional view of the display device inFIG. 1.

FIG. 8 is a diagram for explaining a manufacturing method of the displaydevice.

FIG. 9 is a IX-IX line cross-sectional view of the structure in FIG. 8.

FIG. 10 is a cross-sectional view of a display device in a firstvariation of the embodiment.

FIG. 11 is a cross-sectional view of a display device in a secondvariation of the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, some embodiments will be described with reference to thedrawings. Here, the invention can be embodied according to variousaspects within the scope of the invention without departing from thegist of the invention and is not construed as being limited to thecontent described in the embodiments exemplified below.

The drawings are further schematically illustrated in widths, thickness,shapes, and the like of units than actual forms to further clarifydescription in some cases but are merely examples and do not limitinterpretation of the invention. In the present specification. and thedrawings, the same reference numerals are given to elements having thesame functions described in the previously described drawings and therepeated description will be omitted.

Further, in the detailed description, “on” or “under” in definition ofpositional relations of certain constituents and other constituentsincludes not only a case in which a constituent is located just on orjust under a certain constituent but also a case in which anotherconstituent is interposed between constituents unless otherwisementioned.

FIG. 1 is a plan view of a display device in an embodiment. The displaydevice is actually folded to be used, FIG. 1 is a developed view of thedisplay device before it is folded. FIG. 2 is a schematic view of thedisplay device in use. FIG. 3 is a III-III line schematiccross-sectional view of the display device in FIG. 2.

The display device includes a display DSP. A. spacer SP is placed insidecurvature, preventing the display DSP from being bent too much. Thedisplay DSP has flexibility and is folded outside the display area DA.The display DSP has an integrated circuit chip CP mounted thereon fordriving an element to display images. A flexible printed circuit boardFP is connected to the display DSP outside the display area DA.

The display device may be an organic electroluminescence display device.The display device has a display area DA for displaying the images. Thedisplay area DA displays a full-color image by forming full-colorpixels, each of which consists of unit pixels (subpixels) in soniccolors such as red, green, and blue.

FIG. 4 is a IV-IV line cross-sectional view of the display device inFIG. 1. A resin substrate 10 is formed from polyimide. Or, other resinmaterials can be used as long as the materials have satisfactoryflexibility for a sheet display or a flexible display. A reinforcingfilm is put on a back of the resin substrate 10 with apressure-sensitive adhesive 12 interposed therebetween.

A barrier inorganic film 16 (undercoat layer) is laminated on the resinsubstrate 10. The barrier inorganic film 16 has a three-layer laminatedstructure of a silicon oxide film 16 a, a silicon nitride film 16 b, anda silicon oxide film 16 c. The silicon oxide film 16 a of the lowestlayer is for improving close-fitting properties with the resin substrate10; the silicon nitride film 16 b of the middle layer is a blocking filmfrom external moisture and impurities; the silicon oxide film 16 c ofthe uppermost layer is another blocking film to prevent hydrogen atomsin the silicon nitride film 16 b from diffusing on a side of asemiconductor layer 18 of a thin film transistor TR. Such a structure,however, is not essential. Another layer or a two-layer laminate isapplicable thereto.

An additional film 20 may be formed in response to an area where thethin film transistor TR is formed. The additional film 20 may curb acharacteristic change of the thin film transistor TR due to lightintrusion from its channel back or may provide the thin film transistorTR with a backgating effect by being formed from a conductive materialto apply a certain potential. In the embodiment, after the silicon oxidefilm 16 a is formed, the additional film 20 is formed in an island shapecorresponding to the area where the thin film transistor TR is formed,and then the silicon nitride film 16 b and the silicon oxide film 16 care laminated, whereby the additional film 20 is sealed in the barrierinorganic film 16. Alternatively, The additional film 20 may be formedon the resin substrate 10, prior to forming the barrier inorganic film16.

The thin film transistor TR is on the barrier inorganic film 16. Apolysilicon thin film transistor is illustrated and only an N-chtransistor is herein shown but a P-ch transistor may be simultaneouslyformed. The semiconductor layer 18 of the thin film transistor TR has astructure where a low concentration impurity area is provided between achannel area and a source/drain area. A silicon oxide film is hereinused for a gate insulating film 22. A gate electrode 24 is a part of afirst wiring layer W1 made from MoW. The first wiring layer W1 includesa first storage capacitor line CL1 in addition to the gate electrode 24.A part of a storage capacitor Cs is formed between the first storagecapacitor line CL1 and the semiconductor layer 18 (source/drain area)with the gate insulating film 22 interposed therebetween.

An interlayer dielectric 26 (silicon oxide film and silicon nitridefilm) is laminated on the gate electrode 24. A second wiring layer W2,which includes portions for the source/drain electrode 28, is on theinterlayer dielectric 26. A three-layer laminated structure made fromTi, Al, and Ti is herein employed. The first storage capacitor line CL1(part of the first wiring layer W1) and a second storage capacitor lineCL2 (part of the second wiring layer W2) constitute another portion ofthe storage capacitor Cs, with the interlayer dielectric 26 interposedtherebetween.

A flattening organic film 30 covers the source/drain electrode 28.Resins such as photosensitive acrylic are used for the flatteningorganic film 30 because of superior surface flatness, compared withinorganic insulation materials formed by chemical vapor deposition(CVD).

The flattening organic film 30 is removed at a pixel contact portion 32and has an indium tin oxide (ITO) film 34 formed thereon. The indium tinoxide film 34 includes a first transparent conductive film 34 a and asecond transparent conductive film 34 b separated from each other.

The second wiring layer W2, which has its surface exposed by removingthe flattening organic film 30, is covered with the first transparentconductive film 34 a. A silicon nitride film 36 is on the flatteningorganic 30, covering the first transparent conductive film 34 a. Thesilicon nitride film 36 has an opening at the pixel contact portion 32.A pixel electrode 38 is laminated on and connected to the source/drainelectrode 28 through the opening. The pixel electrode 38 is a reflectiveelectrode and has a three-layer laminated structure of an indium zincoxide film, an Ag film and an indium zinc oxide film. Instead of theindium zinc oxide film, an indium tin oxide film can be used. The pixelelectrode 38 extends laterally from the pixel contact portion 32 and toabove the thin film transistor TR.

The second transparent conductive film 34 b is adjacent to the pixelcontact portion 32 and under the pixel electrode 38 (further below thesilicon nitride film 36). The second transparent conductive film 34 b,the silicon nitride film 36, and the pixel electrode 38 overlap with oneanother, thereby forming an additional capacitance Cad.

An insulation organic film 40, which is called a bank (rib) for apartition of adjacent pixel areas, is on the flattening organic film 30and over the pixel contact portion 32, for example. Photosensitiveacrylic may be used for the insulation organic film 40 same as theflattening organic film 30. The insulation organic film has an openingfor exposing a surface of the pixel electrode 38 as a light-emittingregion. The opening should have an edge in a gently declined shape. Asteep shape of the opening edge may cause insufficient coverage of anorganic electroluminescence layer 42 formed thereon.

The flattening organic film 30 and the insulation organic film 40 are incontact with each other through an opening in the silicon nitride film36 between them. This makes it possible to remove moisture and gasdesorbed from the flattening organic film 30 through the insulationorganic film 40 during heat treatment after the insulation organic film40 is formed.

An organic electroluminescence layer 42, made from organic materials,for example, is laminated on the pixel electrode 38. The organicelectroluminescence layer 42 may be a single layer or may have astructure where a hole transport layer, a light-emitting layer, and anelectron transport layer are laminated in this order from the pixelelectrode 38. These layers may be formed by vapor deposition or byapplication after solvent dispersion, may be selectively formed forrespective pixel electrodes 38 (respective sub-pixels), or may be formedentirely over the display area DA. The overall formation results in astructure for emitting white light, from which desired color wavelengthportion is extracted at every sub-pixel through a color filter (notshown in the figures).

A counter electrode 44 is on the organic electroluminescence layer 42.Due to a top emission structure employed herein, the counter electrode44 is transparent. A Mg layer and an Ag layer may be formed to be asthin a film as outgoing light from the organic electroluminescence layer42 can pass. In comply with the forming order of the organicelectroluminescence layer 42, the pixel electrode 38 is an anode, andthe counter electrode 44 is a cathode. The plurality of pixel electrodes38, the counter electrode 44, and the organic electroluminescence layer42 between central portion of the respective pixel electrodes 38 and thecounter electrode 44 constitute light-emitting element layer 46. Thelight-emitting element layer 46 includes the display area DA fordisplaying the images.

A sealing layer 48 is on the counter electrode 44 to cover thelight-emitting element layer 46. The sealing layer 48 may serve toprevent external moisture intrusion into the organic electroluminescencelayer 42 formed thereunder, requiring high gas barrier properties. Thesealing layer 48 has a laminated structure where an organic film 50interposed between a first inorganic film and a second inorganic film 54(e.g. silicon nitride film) thereover and thereunder. The firstinorganic film 52 and the second inorganic film 54 are configured to bein contact with and overlap with each other around the organic film 50(FIG. 6).

A touch sensing layer 56, a protective layer 58, and a polarizing plate60 (e.g. circularly polarizing plate) are laminated on the sealing layer48. The touch sensing layer 56 has some transmitting electrodes Tx andsome receiving electrodes Rx, mutually intersected. The counterelectrode 44 may be divided into some portions to be used fortransmitting electrodes, making it possible to omit the transmittingelectrodes Tx.

FIG. 5 is a circuit diagram of the display device in FIG. 1. The circuitincludes a plurality of scan lines GL connected to a scanning circuit GDand a plurality of signal lines DL connected to a signal drive circuitSD. The signal drive circuit SD is in the integrated circuit chip CP inFIG. 1. A pixel PX is an area surrounded by adjacent two scan lines GLand adjacent two signal lines DL. The pixel PX has the thin filmtransistor TR as a drive transistor, a thin film transistor TR2 as aswitch, and a storage capacitor Cs. By implying gate voltage to the scanline GL, the thin film transistor TR2 is turned ON, whereby a videosignal is supplied from the signal line DL, and charge is stored in thestorage capacitor Cs. By storing the charge in the storage capacitor Cs,the thin film transistor TR is turned ON, passing a current from a powerline PWL to the light-emitting element OD. With the current, thelight-emitting element OD emits light.

FIG. 6 is a VI-VI line cross-sectional view of the display device inFIG. 1. An array substrate 62 in FIG. 6 stands for all the layers belowthe flattening organic film 30 in FIG. 4. The interlayer dielectric 26is the uppermost layer of the array substrate 62, outside the displayarea DA. The flattening organic film 30 is on the array substrate 62.The flattening organic film 30 is formed all over the display area DA,with peripheries outside the display area DA. The flattening organicfilm 30 is covered with the silicon nitride film 36. The silicon nitridefilm 36 closely adheres to the array substrate 62 (interlayer dielectric26 of the uppermost layer in FIG. 4), outside the flattening organicfilm 30, with the flattening organic film 30 sealed therebetween,preventing moisture intrusion.

A first bank 64 is provided to be spaced from the flattening organicfilm 30. The first bank 64 surrounds the flattening organic film 30. Asecond bank 66 is additionally provided to be spaced from the first bank64. The second bank 66 surrounds the first bank 64. The first bank 64and the second bank 66 are made from materials same as the flatteningorganic film 30 and are simultaneously made. Or, the flattening organicfilm 30, the first bank 64, and the second bank 66 are formed, with theorganic layer separated. The silicon nitride film 36 continuously coversthe first bank 64 and second bank 66, from above the flattening organicfilm 30.

The light-emitting element layer 46 in FIG. 4 extends outward from thedisplay area DA. The sealing layer 48 is on the light-emitting elementlayer 46. The sealing layer 48 includes the first inorganic film 52, theorganic film 50 laminated on the first inorganic film 52, and the secondinorganic film 54 laminated on the organic film 50. The first inorganicfilm 52 and the second inorganic film 54, between which the organic film50 is interposed, are in contact with each other around the organic film50 (FIG. 6).

FIG. 6 shows that the organic film 50 has an upper surface sloping downat a peripheral portion in an outward direction, with less thicknesscloser to a tip. Due to a foreign object 68 at the peripheral portion ofthe organic film 50, the organic film 50 is unable to cover the foreignobject 68, making it possible to make a hole in the second inorganicfilm 54.

The sealing layer 48 includes a third inorganic film 70. The thirdinorganic film 70, without overlapping with the display area DA, coversthe peripheral portion of the organic film 50. The third inorganic film70 is laminated at least one of over and under the second inorganic film54. The third inorganic film 70 is entirely in contact with the secondinorganic film 54. The third inorganic film 70 includes some layers. Thethird inorganic film 70 can prevent deterioration of barrier performanceof the sealing layer 48.

The first bank 64 surrounds the organic film 50. The first inorganicfilm 52 and the second inorganic film 54 have respective tips beyond thefirst bank 64 from the organic film 50. The respective tips are closerto an edge of the array substrate 62 than the first bank 64. The firstinorganic film 52 and the second inorganic film 54 have the respectivetips above the second bank 66. The third inorganic film 70 has a tipabove the first bank 64.

FIG. 7 is a VII-VII line cross-sectional view of the display device inFIG. 1. The array substrate 62 has a trace 72 for electrcal connectionwith the integrated circuit chip CP and the flexible printed circuitboard FP. As shown in FIGS. 2 and 3, due to the display DSP being bent,a curvature area thereof does not have the flattening organic film 30.FIG. 7 illustrates that the third inorganic film 70 is formed on anexternal connection side.

FIG. 8 is a diagram for explaining a manufacturing method of the displaydevice. In the embodiment, multiple displays DSP are obtained from onelarge substrate 74. Specifically, the resin substrate 10 in FIG. 4 isprepared without being cut and then each layer is formed.

During processes of forming the sealing layer 48 in FIGS. 6 and 7, thefirst inorganic film 52 and the second inorganic film 54 are laminatedto entirely cover each display DSP and etched using the protective layer58 as a mask. The protective layer 58 as a resin film is formed byapplying photolithography. The second bank 66 serves to preventmaterials of the protective layer 58 from flowing outward.

The first inorganic film 52 and the second inorganic film 54 are etchedto expose the trace 72 as shown in FIG. 7 for electrical connection withthe integrated circuit chip CP and the flexible printed circuit boardFP. FIG. 8 illustrates that each display DSP at its peripheral portionhave an area (hatched area) where neither the first inorganic film 52nor the second inorganic film 54 is formed. During the formation of theorganic film 50 in FIGS. 6 and 7, the first bank 64 serves to preventresins from flowing outward.

The third inorganic film 70 is also patterned by etching after beingformed to entirely cover each display DSP. The third inorganic film 70may be formed by CVD from SiN or SiON with high barrier properties ormay be formed by atomic layer deposition (ALD) method with highforeign-object-coating performance. The third inorganic film 70 ispatterned to surround the display area DA.

FIG. 9 is a IX-IX line cross-sectional view of the structure in FIG. 8.In the embodiment, due to the etching mask being used, the thirdinorganic film 70 has no portion at a part of a frame area around thedisplay area DA. The third inorganic film 70, in a plan view, has adiscontinuous shape in the frame area, except for the part thereof,around the display area DA. By contrast, FIGS. 6 and 7 arecross-sectional views of an area including the third inorganic film 70.The manufacturing method includes other ways obvious from explanation ofthe display device.

[Variation]

FIG. 10 is a cross-sectional view of a display device in a firstvariation of the embodiment. In this example, the first inorganic film152, the second inorganic film 154, and the third inorganic film 170 arepatterned by film formation using a mask. Due to no etching being done,no second bank is formed to prevent flow of the protective layer 58.

FIG. 11 is a cross-sectional view of a display device in a secondvariation of the embodiment. In the example, the sealing layer 248includes the second organic film 276 interposed between the secondinorganic film 254 and the third inorganic film 270. The third inorganicfilm 270 is in contact with the second inorganic film 254, outside thesecond organic film 276. Forming the second organic film 276 can furtherimprove foreign-object-coating performance.

The electronic device is not limited to the organic electroluminescencedisplay device but may be a display device with a light emitting elementdisposed in each pixel, such as a quantum-dot light emitting diode(QLED), or a liquid crystal display device.

While there have been described what are at present considered to becertain embodiments, it will be understood that various modificationsmay be made thereto, and it is intended that the appended claims coverall such modifications as fall within the true spirit and scope of theinvention.

1-9. (canceled)
 10. An electronic device comprising: a substrateincluding a first area and a second area surrounding the first area; ahole transport layer, an electron transport layer, and a first organiclayer between the hole transport layer and the electron transport layerdisposed in the first area; and a sealing layer, wherein the sealinglayer includes a first inorganic film, a second inorganic film, anorganic film disposed between the first inorganic film and the secondinorganic film, and a third inorganic film, the first inorganic film,the second inorganic film, and the organic film are disposed in thefirst area and the second area, the third inorganic film has barrierproperties, is formed from SiN or SiON, and is disposed in the secondarea without overlapping with the first area, the first inorganic film,the second inorganic film, and the organic film are disposed between thethird inorganic film and the substrate in the second area, and the firstinorganic film and the second inorganic film include contacting portionsthat are in contact with each other in the second area, and a lateralextent in a direction parallel with a top surface of the substrate of anend portion of the third inorganic film is on the contacting portions,wherein the third inorganic film does not extend beyond the contactingportions in a direction parallel with the top surface of the substratetoward the second area.
 11. The electronic device according to claim 10,wherein the third inorganic film is laminated over the second inorganicfilm.
 12. The electronic device according to claim 10, wherein the thirdinorganic film is entirely in contact with the second inorganic film.13. The electronic device according to claim 10, wherein the sealinglayer further includes a second organic film interposed between thesecond inorganic film and the third inorganic film, and the thirdinorganic film is in contact with the second inorganic film at a portionwhich is nearer an edge of the substrate than the second organic film.14. The electronic device according to claim 10, wherein the organicfilm has an upper surface sloping down at the second area, and theorganic film is thinner closer to a tip.
 15. The electronic deviceaccording to claim 10, further comprising a bank around the organicfilm, wherein the first inorganic film and the second inorganic filmhave respective tips between the organic film and an edge of thesubstrate, and the third inorganic film has a tip on the bank.
 16. Theelectronic device according to claim 15, further comprising a secondbank around the bank, wherein the first inorganic film and the secondinorganic film have the respective tips on the second bank.
 17. Theelectronic device according to claim 10, wherein the third inorganicfilm includes plural layers.
 18. The electronic device according toclaim 10, wherein the third inorganic film has a discontinuous shape ina frame area around the first area.